The present invention relates generally to appartaus for tracing the outline of an article and deals more specifically with apparatus for tracing the inner periphery of an eyeglass frame lens opening and for producing a number of coordinates each of which represents an associated position along the traced path and which coordinates collectively characterize the size and shape of the traced lens opening in the eyeglass frame.
Conventionally, an optical lens blank is contoured or edged to fit the lens opening in an eyeglass frame by apparatus intended for that purpose. In such edging apparatus, a pattern substantially replicating the size and shape of the lens opening in an associated eyeglass frame is typically used as a guide to control the edging apparatus so that the edged lens properly fits the opening in the frame. Generally, an eyeglass frame manufacturer provides such patterns for each of the different eyeglass frame styles that he sells. These patterns are usually identified and often kept in an inventory maintained by the user of such patterns. In lens edging businesses in which an inventory of patterns is kept, a pattern associated with a given frame style is selected from the inventory, assuming such a pattern is in the inventory, and the pattern is used with edging apparatus to contour an optical lens to fit the given frame style lens opening.
Over the past several years, the proliferation of eyeglass frame styles and an increased number of eyeglass frame manufacturers have made it impractical for those operating from an inventory of patterns to order and maintain a pattern for each of the different eyeglass frame styles due in part to the increased space requirements necessary to store the greater number of different patterns. In addition, the process of selecting a given pattern from the inventory has become more difficult, inconvenient and time consuming. Oftentimes in a large laboratory a given pattern may be in use and not available for selection.
Another problem associated with contouring or edging an optical lens to the size and shape of the lens opening in a given frame in accordance with a pattern associated with the frame is that the frame lens opening associated with a given frame style may not be consistent from frame-to-frame. Occasionally, an optical lens peripherally contoured from a pattern having a nominal lens opening shape and supplied for a given frame style may not properly fit the lens opening of an actual frame of that style.
It would be desirable therefore to overcome the abovementioned problems associated with using a lens pattern for contouring optical lenses not to supply any such patterns in advance of their need but to instead generate a pattern immediately before the contouring or edging operation by tracing the inner periphery of the lens opening of the actual frame with which the pattern is to be used.
A number of methods and devices are used for making a pattern either directly or indirectly from a frame or from a tracing of the frame lens opening. It is usually required that the frame lens opening be properly centered so that the mechanical center of a pattern corresponding to the size and shape of the associated lens opening coincide with the boxing center of the lens shape when the boxing measurement system is used to dimension a lens opening, lens or pattern.
The boxing center is defined as the center of the smallest rectangle which encloses the lens shape using horizontal and vertical lines. The pattern size or A dimension is defined as the distance between the two vertical sides of the box. The distance between the top and bottom of the box is the vertical or B dimension of the pattern. Because a very small error of even a few tenths of a millimeter in centering a pattern can result in an improper fitting lens, a grid like scale sometimes printed on a pattern blank and comprised of measured distances left, right, up and down from an origin is used to aid in the proper centering of the frame lens opening. Once the frame is centered, the lens opening shape is traced and the pattern blank cut along the marked outline. Any roughness in the pattern edge is smoothed with a file or wheel grinder. A pattern made using the above described method cannot be assured to have the same size as the frame lens opening unless compensation is made for the thickness of the tracing pen and the depth of the eyewire groove among others.
The foregoing method for tracing a frame lens opening to determine the size and shape of the lens opening requires a high degree of skill, is time consuming and subjects a resultant pattern made from the tracing to possible error.
An object of the present invention is therefore to overcome the foregoing problems and limitations by providing apparatus for tracing the inner periphery of the lens opening in an eyeglass frame to produce for each of a number of sensed positions along the tracing path a set of coordinates that define the path and collectively dimensionally characterize the size and shape of the traced lens opening.
A further object of the present invention is to provide apparatus for tracing the outer periphery of a lens or pattern to produce for each of a number of sensed positions along the tracing path a set of coordinates that define the path and collectively characterize the size and shape of the traced lens or pattern.
Another object of the present invention is to store in a memory the set of coordinates characterizing the size and shape of the lens opening associated with a given frame for subsequent retrieval as needed.
Yet another object of the present invention is to provide apparatus for tracing the inner periphery of a lens opening in an eyeglass frame wherein the apparatus is relatively inexpensive, easy to use, reliable and capable of accurately replicating a tracing result.